Effect of Cucumber mosaic virus infection on aphid colony development on aphid colony development

Knowing the tritrophic interactions between plant-virus-insect is important in developing sustainable pest management practices. Myzus persicae is a well-known plant viral vector which can transmit over 40 plant viruses. We studied the impact of Cucumber mosaic virus (CMV) infection in Nicotiana tabacum on the colony development of M. persicae to understand how plant virus infection can affect vector growth and reproduction. Aphid growth, reproduction and fecundity were significantly affected by the virus infection. The mean relative growth rate of M. persicae on healthy plants was 0.29 mg –1 · mg –1 · day –1 and was significantly higher than that of CMV-infected plants (0.23 mg –1 · mg –1 · day –1 ). In contrast, the percentage of survival was significantly higher on CMV-infected plants. The estimated survival percentages of aphids at 20 days after introduction to CMV-infected and healthy plants were 55.8 and 25.8%, respectively. Therefore, the total population of aphids on CMV-infected plants was significantly higher on the 25th day after the introduction of aphids. The total population of aphids on the CMV-infected plants was 1,225 compared to that of healthy plants which was 713. Similarly, mean fecundity over a 30 day observation period was 61.25 and 35.65 for aphids grown on CMV-infected and healthy plants, respectively. Jasmonic acid (JA) upstream gene OPR3 and downstream gene COI1 was measured to quantify the changes in JA expression in the plants under the virus infection. Both genes tested were significantly downregulated in CMV-infected plants. From our results, it was evident that the JA related insect resistance was reduced in CMV-infected plants and hence aphid colony development was increased.